Kotlin协程处理错误和实现

在本地范围内启动协程是一个很好的实践，它可以在支持生命周期的类(例如Presenter或ViewModel)中实现.您可以使用下一种方法传递数据:

1. 在单独的文件中创建sealed Result类及其继承者:

   sealed class Result<out T : Any>
   class Success<out T : Any>(val data: T) : Result<T>()
   class Error(val exception: Throwable, val message: String = exception.localizedMessage) : Result<Nothing>()
   

2. Make onUserLogin function suspendable and returning Result in RepositoryInterface and Repository:

   suspend fun onUserLogin(loginRequest: LoginRequest): Result<LoginResponse> {
       return apiInterface.makeLoginCall(loginRequest)
   }
   

3. 根据以下代码更改APIInterface和APIInterfaceImpl中的makeLoginCall功能:

   suspend fun makeLoginCall(loginRequest: LoginRequest): Result<LoginResponse> {
       if (isInternetPresent()) {
           try {
               val response = MyRetrofitInterface?.loginRequest(loginRequest)?.await()
               return Success(response)
           } catch (e: Exception) {
               return Error(e)
           }
       } else {
           return Error(Exception(Constants.NO_INTERNET))
       }
   }
   

4. 使用Presenter的下一个代码:

   class Presenter(private val repo: RepositoryInterface,
                   private val uiContext: CoroutineContext = Dispatchers.Main
   ) : CoroutineScope { // creating local scope
   
       private var job: Job = Job()
   
       // To use Dispatchers.Main (CoroutineDispatcher - runs and schedules coroutines) in Android add
       // implementation 'org.jetbrains.kotlinx:kotlinx-coroutines-android:1.0.1'
       override val coroutineContext: CoroutineContext
           get() = uiContext + job
   
       fun detachView() {
           // cancel the job when view is detached
           job.cancel()
       }
   
       fun login() = launch { // launching a coroutine
           val request = LoginRequest()
           val result = repo.onUserLogin(request) // onUserLogin() function isn't blocking the Main Thread
   
           //use result, make UI updates
           when (result) {
               is Success<LoginResponse> -> { /* update UI when login success */ } 
               is Error -> { /* update UI when login error */ }
           }
       }
   }
   

EDIT个

We can use extension functions on Result class to replace when expression:

inline fun <T : Any> Result<T>.onSuccess(action: (T) -> Unit): Result<T> {
    if (this is Success) action(data)
    return this
}
inline fun <T : Any> Result<T>.onError(action: (Error) -> Unit): Result<T> {
    if (this is Error) action(this)
    return this
}

class Presenter(...) : CoroutineScope {

    // ...

    fun login() = launch {
        val request = LoginRequest()
        val result = repo.onUserLogin(request) 

        result
            .onSuccess {/* update UI when login success */ }
            .onError { /* update UI when login error */ }
    }
}